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galaxyman
Pooh-Bah
Reged: 04/04/05
Posts: 1207
Loc: Limerick, Pa
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Quote:
You really should consider spending ~$120 and getting a Sky Quality Meter. That takes much of the guesswork out of evealuating your site.
To get back to the original question, yes a 12" will show more detail than a 8" IF it is of equivalent optical quality and basic design. I have both an 8" APO refractor and a 12.5" Dob, and in this case the difference is not real extreme, but it is still very noticable: more like comparing a 10" Dob to a 12" Dob. The 8" APO definitely outperforms a 9.25" SCT (Celestron)and a 10" SCT (Meade), but the overall brightness of the 12.5" Discovery Dob is ahead of the refractor (as it should be). My former Meade SN-10 also did better on DSOs w/r brightness, but not in image sharpness or contrast.
Rodger
We are kind in the same boat.
I agree, the refractor shows incredible detail for 8", but my 12.5 dob (Parks optics) has a notch above just from the size difference.
I am a huge fan of a 12.5" dob, in which I consider the baby of the big dobs. Deep sky really starts to take off at this size.
Karl
E.O.H.
Chesmont Astronomical Society
22" f/4.5 Dob
12.5" f/4.8 Dob
8" f/9 refractor (The Beast)
6" f/6.5 refractor (Mini-Beast)
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So many galaxies, so little time!
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JoeBlow
member
Reged: 11/20/06
Posts: 68
Loc: Australia
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boatstar,
I will definitely be having a look at NGC 1300 at the next available opportunity. Thanks.
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GSO 12" f5 dob
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BillFerris
Carpal Tunnel
Reged: 07/17/04
Posts: 2634
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Quote:
Is M51 the easiest galaxy to make out spiral structure? Is there a Southern Hampshire equivalent of M51?
If it's not the northern sky's most prominent spiral, it's certainly in the top five. Of the galaxies I observed with my old 10 inch, I'd rate M51 as having the most obvious spiral structure. Here, are some galaxies that show good spiral structure in moderate aperture from mid-northern latitudes.
M33
M51A (NGC 5194)
M83
M91
M100
M101
NGC 6946
NGC 7479
My southern sky observing has been limited to what's visible from +35 degrees north. But here are a couple of fine spirals that should look fairly impressive from your end of the globe.
NGC 613
NGC 1365
Good hunting,
Bill in Flag
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Grand Canyon Adventure
Lowering the Threshold
18" Obsession
4.5" Meade 4500
10x50 Swift Audubon
Cosmic Voyage
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Jeff Young
Post Laureate
Reged: 08/04/05
Posts: 3260
Loc: Ireland
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David & Don --
-Great- tips on inferring details and leading questions. I've started to discover some of these on my own (although the shape-change on averted-vs-direct vision hadn't occurred to me yet -- I can't wait to try that one out.)
I have discovered, for instance, that when I describe what features I can see (dimmer areas, sharp cutoffs, shape when stationary vs. shape when OTA is bumped), they often match the DSS images, even if I wouldn't have been able to say "spiral" or "arms" or whatever. I think part of the "training" is learning to internalize larger features based on a few vague details.
Again, very helpful posts, guys.
Cheers,
-- Jeff.
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Nikon 18x70s / UA Millennium Colorado:
Solarscope SF70 / TV Pronto / AP400QMD Coronado SolarMax40 DS / Bogen 055+3130
APM MC1610 / Tak FC-100 / AP1200GTO Tak Mewlon 250 / AP600EGTO
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Jeff Lee
sage
Reged: 09/17/06
Posts: 420
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Hi:
One more suggestion. Is your collimation spot on? To get really excellent viewing from a SCT, you need to make sure that you've done the third step, which is the airy disks at say 400X or so (obviously needs a night of great seeing).
One night I did this and then viewed saturn, the details were significantly better than with just an out of focus collimation.
Many SCT's are not spot on, and it makes a huge difference. Of course something like Bob's Knobs makes it easy if the viewing is good enough.
Just a thought.
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Jeff Lee
C90,C5,C8, 10 x 50's
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Achernar
Post Laureate
Reged: 02/25/06
Posts: 3837
Loc: Alabama, USA
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It's one of the easiest tos ee sprial arms in, but M-31, M-33, NGC-6946, M-106 and other bright galaxies also show spiral arms from dark sites. NGC-galaxies such as NGC-2903 will really show them too. It's a matter of catching them on dark, clear nights, and sometimes it does take repeated observations until you get a glimpse. I've also found that often I see spiral arms without realizing it at first, but when I compare a sketch to a photo, features I sketch line up with spiral arms in the photos. You really need to take your scope to a black sky site, it'll be for those who have to make do with light polluted skies as if all of a sudden their telescopes doubled or tripled in aperture. As for M-83, you did see the spiral arms, they can and do show up as nebulous patches. I've seen the same effect before in galaxies such as M-61.
Taras
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10-inch F/4.5 Discovery Dob
6-inch F/8 Homebuilt Dob
4 1/4-inch F/4 Homebuilt reflector
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